Address review feedback on Pyrefly migration

Drop redundant typecheck problem matcher; use pyrefly --output-format github in CI. Add types-networkx to typecheck deps, trim ignore-missing-imports to optional imports only, and document temporarily disabled Pyrefly-only error kinds. Restore universal env pins (Python 3.10) while swapping mypy for pyrefly in dev/typecheck env files.

Author: rosspeili

.github/problem-matchers/README.md

@@ -28,11 +28,6 @@ made available under the terms of the MIT license.
 
 -   [`pytest.json`](https://github.com/liskin/gh-problem-matcher-wrap/blob/master/problem-matchers/pytest.json)
 
-The typecheck problem matcher matches Pyrefly's text and GitHub Actions output
-formats used by `check/typecheck`.
-
--   [`typecheck.json`](./typecheck.json)
-
 The actionlint problem matcher JSON file came from the
 [actionlint](https://github.com/rhysd/actionlint/blob/v1.7.7/docs/usage.md)
 documentation (copied on 2025-02-12, version 1.7.7). Actionlint is made

.github/problem-matchers/typecheck.json

@@ -96,9 +96,7 @@ jobs:
           check/pylint -j 0
 
       - name: Check type declarations
-        run: |
-          echo '::add-matcher::.github/problem-matchers/typecheck.json'
-          check/typecheck --output-format github
+        run: check/typecheck --output-format github
 
   pytest:
     name: Unit tests

.github/workflows/ci.yaml

@@ -1 +1,3 @@
 pyrefly
+
+types-networkx